STP1494

The Natural Cement Revival

Although lime has long been an important component in masonry construction, experienced masons working on the restoration of historic buildings in the United States cannot help but notice that some American mortars are very different from the traditional lime mortars used in Europe. American mortars, as found in many 19th century commercial, industrial and government buildings, are clearly tougher and more tenacious than the typical lime mortars. While some claimed that this is due to the importation of hydraulic limes from Europe, study of the period's plentiful documentation reveals that natural cement was the most widely used hydraulic binder in its time. This paper retraces key steps in the search for the history of natural cement use in the United States, and in rediscovering its origins, production methods and use. Ultimately, these steps led to the commercial reintroduction of natural cement for use in historic restoration.